The initial recovery of base metal values from deep-sea manganese ore nodules mined from the ocean floor has prompted a search for efficient methods of extracting the valuable metal values which are entrapped by large quantities of manganese.
In order to render the deep-sea nodules leachable, the manganese dioxide (MnO.sub.2) in the nodules must be broken down so that the leach liquor can reach the metal values of interest. One known method of breaking down the manganese dioxide is reduction. Indeed, several reduction schemes have been developed, one of which is a single stage fluid bed reduction scheme.
In the single stage fluid bed reduction process, Bunker C oil is partially combusted with air to provide the fluidizing gas and a reducing atmosphere. A disadvantage of this method is poor fuel gasification and excessive carbon deposition at the operating conditions required to reduce nodules. The use of ore pre-soaked with oil is also unexceptable for the same reasons.
A gas reduction route essentially free of carbon deposition is known; however, the cost of the reducing gas required for this scheme renders it economically unexceptable.